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Antibodies and B cells recognising citrullinated proteins display a broad cross-reactivity towards other post-translational modifications
  1. T Kissel1,
  2. S Reijm1,
  3. LM Slot1,
  4. M Cavallari2,
  5. CM Wortel1,
  6. RD Vergroesen1,
  7. G Stoeken-Rijsbergen1,
  8. JC Kwekkeboom1,
  9. ASB Kampstra1,
  10. EWN Levarht1,
  11. JW Drijfhout3,
  12. H Bang4,
  13. KM Bonger5,
  14. GMC Janssen6,
  15. PA van Veelen6,
  16. TWJ Huizinga1,
  17. HU Scherer1,
  18. M Reth2,
  19. REM Toes1
  1. 1 Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
  2. 2 Department of Biology III (Molecular Immunology), Freiburg University, Freiburg, Germany
  3. 3 Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, The Netherlands
  4. 4 Orgentec Diagnostika, Mainz, Germany
  5. 5 Department of Biomolecular Chemistry and Synthetic Organic Chemistry, Radboud University, Nijmegen, The Netherlands
  6. 6 Center for Proteomics and Metabolomics, Leiden University Medical Center, Leiden, The Netherlands
  1. Correspondence to T Kissel, Rheumatology, Leiden University Medical Center, Leiden 2300, Netherlands; T.kissel{at}


Objective Autoantibodies against antigens carrying distinct post-translational modifications (PTMs), such as citrulline, homocitrulline or acetyllysine, are hallmarks of rheumatoid arthritis (RA). The relation between these anti-modified protein antibody (AMPA)-classes is poorly understood as is the ability of different PTM-antigens to activate B-cell receptors (BCRs) directed against citrullinated proteins (CP). Insights into the nature of PTMs able to activate such B cells are pivotal to understand the ‘evolution’ of the autoimmune response conceivable underlying the disease. Here, we investigated the cross-reactivity of monoclonal AMPA and the ability of different types of PTM-antigens to activate CP-reactive BCRs.

Methods BCR sequences from B cells isolated using citrullinated or acetylated antigens were used to produce monoclonal antibodies (mAb) followed by a detailed analysis of their cross-reactivity towards PTM-antigens. Ramos B-cell transfectants expressing CP-reactive IgG BCRs were generated and their activation on stimulation with PTM-antigens investigated.

Results Most mAbs were highly cross-reactive towards multiple PTMs, while no reactivity was observed to the unmodified controls. B cells carrying CP-reactive BCRs showed activation on stimulation with various types of PTM-antigens.

Conclusions Our study illustrates that AMPA exhibit a high cross-reactivity towards at least two PTMs indicating that their recognition pattern is not confined to one type of modification. Furthermore, our data show that CP-reactive B cells are not only activated by citrullinated, but also by carbamylated and/or acetylated antigens. These data are vital for the understanding of the breach of B-cell tolerance against PTM-antigens and the possible contribution of these antigens to RA-pathogenesis.

  • rheumatoid arthritis
  • autoantibodies
  • B cells

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  • Handling editor Josef S Smolen

  • TK and SR contributed equally.

  • Contributors All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be published.

  • Funding This work has been financially supported by ReumaNederland (17-1-402), the IMI funded project RTCure (777357), ZonMw TOP (91214031) and Target-to-B (LSHM18055-SGF). HUS is the recipient of a NWO-ZonMW clinical fellowship (90714509), a NWO-ZonMW VENI grant (91617107), a ZonMW Enabling Technology Hotels grant (435002030) and received support from the Dutch Arthritis Foundation (15-2-402 and 18-1-205). M.Reth is funded by the Excellence Initiative of the German Federal and State Governments (EXC 294) and by the DFG through TRR130-P02 and the RO1 grant (A031503). P.A. van Veelen is funded by an Investment Grant NWO Medium (91116004), which is (partially) financed by ZonMw.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.